Control system



july 19, 1949. J. s. MAIDLOW, JR., ET AL 2,475,313

CONTROL SYS TEM Filed Oct. 16, 1943 '2 Sheets-Sheet 1 July 19, 1949.

Filed Oct. 16, 1943 J. S. MAIDLOW, JR., ET AL.

CONTROL SYSTEM 2 'sheets-sheet 2 3 2 Tsen/Mw.

/0 Mrs fname Patented July 19, 1949 CONTROL SYSTEM John S. Maidlow, Jr.,and James M. Reynolds, United States Army Application October 16, 1943,Serial No. 506,564)

In Australia February 25, 1943 5 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to us ofany royalty thereon.

This invention relates to radio communication, and more particularly toimprovements in radio telegraph systems employing means forautomatically transmitting signals and automa-tin cally recordingsignals in print at va receiving station.

Radio signals as generally received are too feeble to actuate a relay,unassisted, for the purpese of controlling a telegraph printing deviceof the class known as Teletype. This inadequacy of the radio signal forthe desired purpose is also aggravated by the radio phenomena known asfading and climatic conditions, which may, if occurring during thesignalling period, cause loss of an impulse and the mutilation of thetransmission code.

It is, therefore, an object of this invention to provide a novelelectrical circuit and arrangeof elements whereby a received radiosignal is suiciently amplified to actuate a relay contrcliing atelegraph printing device.

A further object of the invention is the provision of a radio telegraphsystem in which the operation of a recording printer at a receivingstation automatically causes a radio transmitter, which is already inoperation at the receiving station, to retransmit the signal to theoriginal transmitting station Where the signal is received and a printedrecord made thereof, thus insuring the receipt of the message by theoriginal receiving station.

These and other objects are attained by the novel circuit andarrangement hereinafter described and illustrated in the accompanyingdrawings, forming a part hereof, and in which:

Figure l is a schematic diagram of an electrical circuit embodied in theinvention.

Figure 2 is a diagram of communication system according to theinvention.

Referring to the diagram, a diversity radio reception system is shown toinclude three radio receiving sets I, 2, 3, adapted to receiveinterrupted continuous wave signals. The antennas of the receiving setsare spaced by ten Wave lengths from each other. The audio output of eachreceiver is separately rectified by rectifying (Granted under the actamended April 30, 1928; 370 O. G. 757) l, thereby of March 3, 1883, as

tubes 4, 5, respectively, producing a combined negatively directedvoltage which is passed through a filter to allow only the modulatedfrerduency of the tone transmitted to pass.

The voltage from the iilter is applied to the grid 8 of a direct currentamplifying tube l, the cathode 9 of which is returned to ground throughthe plate circuit il of a vacuum tube Iii of the beam power type.

The output of tube l' is appplied directly to the grid I3 of anothervacuum tube Iii, preferably of the beam power type. Normally with nosignal input to the receivers, no negative voltage is applied to thegrid of the direct current amplifier' l. This allows current to ow inthe amplifier tube l. This current flow places a high bias on tube I 4,keeping the current in the plate circuit of tube I4 extremely low.

When the incoming signal has the proper modulation frequency, negativebias is placed on the grid 8 of tube l', causing the tube to draw lesscurrent, which lowers the bias voltage on the grid of tube I, causingcurrent to ow through the plate circuit of tube I 4.

The plate current change in the direct current amplifier tube 'l ismaintained at a very low value up to a predetermined value of negativegrid voltage by the vacuum tube I0, which has its plate II connected tothe cathode 9 of tube l. The voltage of tube l) is stabilized by theassistg ance of a glow type voltage regulator tube l5. A negative gridvoltage slightly above the predetetrmined negative grid voltagementioned above causes a large change in the plate current of tuberesulting in a great change in the bias of the tube l ffl. This being apositive change causes tube l to draw a large current, A sensitive relayis placed in the plate circuit of tube I4.

In operation the gain of the receivers is adr justed so that the voltageproduced by the noise level is below the critical point of the grid oftube 7. If the incoming modulated continuous wave is above noise levelit will cause the voltage on the grid of the amplifier tube 7 to riseabove the critical point.

In practice, a rIeletype transmitter and receiver is used at eachstation. Two transmitting irequencies are used, one for transmitting anoriginal message, and the other for retransmitting a received messageback to the original transmitting station. The incoming signal isreceived by one or more of the radio receivers, from which it isrectified, filtered and passed to the amplier tube 'I, to produce acurrent in the plate circuit thereof. A small current in tube 'I willcause a low bias of tube I4, and consequently cause the ow of a largecurrent in. the plate circuit of tube I4. This large current is ofsuicient strength to actuate relay 50 which controls a Teletypeapparatus I'Il for receiving' and printing a message. When one stationis receiving its radio transmitter is placed on the air by closingcontacts I9, to send out tone modulated signals. The transmitter is thenkeyed by the Teletype contacts in accordance with the standard Teletypefive unit permutation code to cause the received message to beretransmitted by the transmitter I8 back to the original transmittingstation where itis received and a printed record made thereof by theTeletype apparatus at the original transmitting station.

Thus, when message is transmitted by a iirst station to a secondstation, it is received by thev second station and retransmitted back tothe rst station, where it is received and a printed record made thereof.The rst station then knows d'eiinitely that the message has beenreceived by the second station.

Should at any time the receiving station desire to interrupt. thetransmitting station, the radio transmittingkeying circuit is opened bya manual switch, causing the Teletype machines at both stations to runopen.

.To insure minimum of static interference, either the transmitting orreceiving antennas, or both,` are of the V-beam type.

-The invention having been described, what is claimed is:

1. In a control system, a source of direct current electromotive force;an actuating circuit; a triode including an anode, a cathode and acontrol grid; means connecting said grid and cathode to said actuatingcircuit and said anode and cathode across. said source to place positivepotential at said. anode; said means including means responsive to thecurrent fed to said cathode to greatly reduce said current upon apredetermined drop'thereof and to greatly increase the same upon apredetermined rise thereof from'its said reduced magnitude; a tubehaving a cathode, a controlgrid and an anode; wires connecting thelast-named grid to the negative pole of saidV source and the last-namedcathode tothe first-named cathode; a circuit passing through saidlast-recited anode and cathode, said circuit including a source ofdirect current electromotive force therein; and means to be energizedand deenergized in said last-named circuit.

2. A control system denned in claim 1 in which said'rst-named meanscomprises a tube having anv anode connected to the cathode of saidtriode, a screen grid, and a cathode connected to said actuatingycircuit as well as to the negative pole of the first-named source ofsaid claim l; and means for supplying a constant high voltage positivepotential at said screen grid with respect to thelast-mentioned cathodewhereby the plate current change in the first-named tube of claim 1 ismaintained at a very low value up to a predetermined value of negativegrid voltage and a change beyond said predetermined value effects promptgreat` change in the current.

3. In a control system; a triode having an anode, a control grid and acathode; a second tube=having an anodeconnected to said cathand cathodeof said driven tube, a source oi power, and means to be energized.

fi. In a control system the combination with a circuitincluding thereinmeans to be controlled of an' actuating circuit; a triode including ananode, .a cathode. and a control grid; said grid and cathode beingconnected across said actuating circuit; a single tube for controllingpulses to `the first-named circuit, including an anode and a cathode.connected in said first-named circuit, and a control` grid; a secondcircuit including the series current path of the first-named anode, thefirst-named cathode,l the second-named cathode andthe last-named grid,said series current path including a source fofpolarizedelectricitytherein connected to affect the last-named grid negatively; whereby thelast-named tube will be increased and decreased in conductivityinversely as. the said .triodey said'rst-named circuit includingfthereinavsourceA of power affecting the second-named anode positively; andmeans for increasing the degree of sharpness of said triode in becoming.`conducting and non-conducting in response toV changes in the potentialacross said actuating circuit, the last-named means comprising means inthe cathode circuit of said triode that saturates whenthe triode is notbiased by said actuating. vcircuit.

5( In a control system, the combination with a circuit including`'therein means to be controlled of .an actuatingl circuit; a. triodeincluding an anode, a cathode and a control grid; said grid and cathodebeing connected across said actuating, circuit;` a single tube for.'controlling pulses to the first-.named circuit, including an anode anda cathode connected in said first-named circuit, and a control. grid; asecond circuit including thev series current path of vthe first-namedanode, the Yirst-named cathode, the secondnamed cathode andthelast-named grid, said series current path including. a source oipolarized electricity 4therein connected to aifect the last-named gridnegatively; whereby the lastnamedV tube will' be increased and decreasedin conductivity inversely as the said triode; said rst-na'med circuitincluding therein a source oi power aiecting the second-named anodepositively; and means for increasing the degree of sharpness offsaid'triode in becoming conducting and non-conducting in response to changesin therpotenti'al across said actuating circuit, the last-named meanscomprising a tube having an anode connected to the cathode of saidtriode and a cathode connected to the said actuating circuit, saidlast-named tube including means whereby it is saturated bythe' currentof said triode when the latter is not actuated by said actuatingcircuit;

JAMES M. REYNOLDS.

JOHN S. MAIDLOW, JR.

(References on. following page) 5 REFERENCES CITED UNITED STATES PATENTSNumber Name Date Read Jan. 17, 1922 Turner July 4, 1922 Heising Aug. 21,1923 Bennett Sept. 16, 1924 Beverage et al. Aug. 30, 1932 Griflth Aug.22, 1933 Kaliman Dec. 25, 1934 Watson June 4, 1935 Robinson June 21,1938 Number 6 Name Date Spencer et al Jan. 3, 1939 White Aug. 13, 1940Thompson May 13, 1941 Buckingham May 5, 1942 Boughtwood July 28, 1942Brubaker Mar. 9, 1943 OTHER REFERENCES Radio Engineering Handbook by K.Henney, published by McGraw-Hill Book Co., New York city, third edition,copyright 1941, page 582.

Radio Engineers Handbook by F. E. Terman, published by McGraw-H111 BookCo., New York city, rst edition, copyright 1943, page 660.

